The present invention is in the field of computer video systems. More particularly, the present invention relates to various methods of visually testing video systems for degradation of video signals that pass through video systems, as well as methods of compensating for this degradation.
Video systems may include a variety of video sources, including but not limited to computers, video cassette recorders, video cameras, and a variety of display devices, including but not limited to CRT monitors, CRT projectors, LCD projectors, DLP projectors, or other video display devices. The video sources can generate video signals of many types, including but not limited to NTSC, PAL, SECAM, as well as the types produced by computers, such as composite, monochrome analog, RGB, RGBS, RGBHV, RGsB, RsGsB, and any additional video standards developed by IBM for personal computer compatible technology, including but not limited to CGA, EGA, VGA, and SVGA type signals and any other standards developed by industry associations like VESA.
Regardless of the specific types of video signals produced, video signals frequently require processing and manipulation before they reach video display devices. To this end, video switchers, video distribution amplifiers and other equipment, as well as various types of interconnecting cables, are frequently installed between video signal sources and video display devices.
Those ordinarily skilled in the pertinent arts will recognize that after video signals pass through such video system and reach video display devices, the quality of the video signals frequently degrade. The degree and type of degradation of a video signal depends upon the characteristics of components of the circuits through which the video signal is passing. The number of components and the individual characteristics of these components, as well as the characteristics and length of interconnecting cables used to connect said devices together determine the video signal degradation level.
In order to determine the extent to which a particular circuit degrades a video signal, as well as to determine how to compensate for the degradation, it is necessary to compare the original video signal generated by the source, with the video signal received by a video display device after the video signal has passed through such circuit.
Conventionally, this is done by connecting a video display device to a video signal source and observing the original image generated by the original video signal on the screen of the video display device. The video display device can then be connected at the output of the video system and the degraded image generated by the video signal after passing through the video system can be compared to the original image before passing through the video system. A troublesome shortcoming of this method is that a person comparing these two images has to remember what the original image looked like because only one image is viewed at a time, and the original image is not displayed while the degraded image is observed.
It is also possible to use two monitors, one connected to the original video signal and displaying the original image and one connected at the output of the video system and displaying the degraded image. However, those skilled in the pertinent arts will recognize that this method requires close proximity between video signal sources and video display devices, which in many cases is not possible. In addition, different display characteristics of each monitor may provide inaccurate results. Alternatively, one can employ network analyzers which test video systems by measuring various bandwidth characteristics. However, those skilled in the pertinent arts will recognize that network analyzers, aside from being expensive, also require close proximity between video signal sources and video display devices, which in many cases is not possible. In addition, specially trained personnel are required to operate complex network analyzers, who are often in short supply, and expensive.
Accordingly, a clear need exists for an inexpensive and simple method of testing video systems for degradation of video signals that pass through video systems, as well as compensating for the degradation of the video systems in order to provide the highest quality image possible.